1. Field of the Invention
A clamping device for holding one half of a folded jacket against an inclined platen in the operation of a paper stuffing machine.
2. Description of the Prior Art
The clamping device of the present invention was created for use in a machine used for stuffing inserts for the assembly of a newspaper. Typical such machines are manufactured by Sheridan Company, a division of HarrisIntertype, located at Easton, Pa. These machines are known as stuffers; their purpose is to facilitate assembly of a newspaper that constitutes more than one section.
Consider, for example, a Sunday newspaper having a main news section and several additional sections such, for example, as a local news section, a world news section, a travel section, an entertainment section, a magazine section, a book section, a classified advertising section, and a sports section. These papers, as sold to the public, conventionally have one outer section, usually the main news section, referred to as the "jacket" which is folded in half and between the two halves of which the other sections, prefolded, are inserted, fold down. Sometimes the other sections are inserted one after another; sometimes the other sections are inserted as a bundle one inside another. Sometimes there are more than one multisection bundles and sometimes there is a mixture including bundles of sections and single sections one alongside another, all within the jacket.
The Sheridan stuffers are designed to insert these sections either in one another or in a jacket, that is to say, to "stuff" the internal sections into the jacket or into one another and then into the jacket. Stuffers, and particularly Sheridan stuffers, constitute carousels on which a large number of pockets are mounted. Typically, the number of pockets is 24, 48 and 72. A pocket is radially disposed around a center about which the carousel turns. The carousel intermittently shifts the pockets to successive stations where various operations are performed, typically stuffing operations; at a given station, the outer jacket is deposited in a pocket with its fold down and its halves angularly spread and at successive stations various newspaper sections are stuffed into the jacket by dropping the same therein. Typically, the number of stations varies from 4 to 13.
A pocket constitutes a pair of walls defining a V, one of the walls being stationary and being the stationary inclined platen of the pocket, and the other wall being movable from a position in which it forms the V to a position in which the bottom of the V is open to permit the newspaper sections after assembly with the outer jacket to be dropped onto a conveyor belt.
The outer section, i.e. the "jacket" which first is deposited in the pocket is composed of several sheets. It is folded in half and the fold is placed at the bottom of the pocket. Hence, the upper edges of the sheets at the two sides of the pocket are free and lie in juxtaposition only because they are so deposited in the pocket. However, these edges are susceptible to being fanned open if struck by a current of air. They act this way even if the sheets are joined by a fold at one upright edge which would tend to hold the horizontal upper edges of the sheets together adjacent this folded edge. This ability of the upper free edges to move apart is bothersome when a section is being dropped into a jacket in a pocket because as the section descends, either driven down or under its own weight, it creates a downward current of air directed at the free edges. The ensuing movement of the free edges is known as a "breezing open" and is most undesirable since the opening of the individual sheets of the jacket can cause enough movement to have some of the sheets caught by the descending section which folds, rumples or tears them.
To prevent such breezing open, present-day stuffers employ a clamping device, e.g. a clamping finger, for each pocket. Each pocket is provided with a horizontal clamping bar on which, conventionally, a rigid arcuate metal clamping finger is made fast. The clamping bar is oscillated about its longitudinal axis to move the finger from an idle position in which it is clear of the pocket to an operative position in which the tip of the finger presses against the inner surface of the half of the jacket that is lying against the inclined stationary platen.
Because the number of sheets can vary, present-day stuffers provide for an adjustable positioning of the operative location of the clamping finger. The clamping bar is oscillated by a kinematic linkage. Such linkage includes an adjustment, proper manipulation of which determines the operative position of the tip of the clamping finger. It is quite apparent that if the jacket includes a few sheets the operative position of the clamping finger must be quite close to the stationary platen of the pocket. On the other hand, if the jacket includes a large number of sheets, the linkage system must be adjusted so that the tip of the clamping finger in operative position is further from the stationary platen.
The foregoing arrangement for clamping a pocket-located jacket has many disadvantages. One is the noise which accompanies the operation of the clamping device. To better appreciate this problem, it should be pointed out that stuffing machines operate at a high speed, as high as 40,000 assembled newspapers per hour, and up to five inserts are stuffed into each jacket. This means that the fingers are oscillating quite rapidly. Each time that a finger strikes a jacket, there is a loud impact thud.
Another problem, and this is associated with the noise, is that the clamping fingers are supposed to be adjusted to assume a position which is related to the number of sheets in the jacket. Practically, however, the operators of the stuffers often do not make this adjustement, and indeed some older machines do not even have the adjustment, so that the machine runs from day to day without any change in the operative positions of the clamping fingers. A position is set for a very few sheets in a jacket to make certain that it will clamp a jacket having a minimum number of sheets. Accordingly, the noise of the tips of the clamping fingers hitting the stationary platen through the sheets becomes very loud.
This permanent or pseudo-permanent setting of the clamping fingers in a position, when operative, that is proximate to the stationary platen also means that a considerable pressure is exerted on the platen upon every operation of the fingers. It has been found in practice that the repetitive hammering away of the fingers on the platens wears an indentation into the platen. Accordingly, on present-day machines it is quite common to provide an insert in the platen at the zone of impact and to replace the insert from time to time.
Still further, for the same reason, i.e. the substantial force exerted by the tip of the finger on the jacket, the finger from time to time distorts, rips or perforates the sheets of the jacket, which obviously is undesirable.